Electrophotographic process employing a photochromic compound and transparent toner

ABSTRACT

A PROCESS FOR THE FORMATION OF TONER IMAGES WHERE AN ELECROSTATICAL IMAGE IS FORMED ON AN ELECTROPHOTOGRAPHIC SENSITIVE LAYER CONTAINING A PHOTOCHROMIC COMPOUND AND DEVELOPED WITH A TONER TO FORM A TONER IMAGE, THE TONER CONTROLLING THE COLORING OR DISCOLORING OR THE COLOR SHADE OF THE PHOTOCHROMIC COMPOUND IN THE SENSITIVE LAYER.

United States Patent Int. Cl. 663 13/06 US. 01. 96-1 R 17 Claims ABSTRACT OF THE DISCLOSURE A process for the formation of toner images where an electrostatical image is formed on an electrophotographic sensitive layer containing a photochromic compound and developed with a toner to form a toner image, the toner controlling the coloring or discoloring or the color shade of the photochromic compound in the sensitive layer.

This invention relates to a new process for the formation of images.

Substances which absorb light and repeat a reversible color change, are called in general photochromic compounds. These compounds maintain in general stable colorless state without the influence of exciting light such as ultraviolet rays. On irradiating ultraviolet rays thereto, they change into a colored state of different absorption spectrum. The molecules under such colored state return readily to the original colorless state due to their instabilities when the exciting light is removed. While there are known many patents relating. to photo-coloring and -discoloring materials utilizing such reversibility, vice versa, owing to the characteristics said photo-coloring and -discoloring materials exhibit using the photochromic compound could not be preserved as permanent images though they are able to be used for copying temporary images. Further, because the color shade is monochromic, it was impossible to form multi-color images though a shading image might be obtained.

We have found a new process which can be applied to both such temporary and permanent image recording and can vary the color shade. Illustrating more fully this in vention, a photochromic compound is contained in an electrophotographic sensitive layer, whereby a sensitive material is obtained which is a photo-coloring and -discoloring material and has characteristics of an electrophotographic material, whereas the photochromic compound is dispersed in a resinous binder in the previous sensitive material containing the photochromic compound.

That is, said sensitive material is charged electrically in the dark and then exposed image-wise to form a permanent image whereby it is colored by means of ultraviolet rays in quite the same manner as in the previous method and discolored by means of heat or visible rays. The exposure time may be very short because theelectrophotographic sensitivity is much higher than the photosensitivity of photochromism. It is then further treated according to the electrophotographic process of this in-- vention to yield a toner image thereon. If a substance which shows a peculiar interaction with the components in the sensitive layer is selected as a material for forming 3,799,773 Patented Mar. 26, 1974 the toner image, a new copying process is realized as described in detail hereinafter.

According to the way of selection, there are classified the following four groups:

(i) When a colorless image is formed using a toner of transparent resin free from color pigment (which may contain e.g. extender) in which the coloring of photochromic compound is hindered, the photochromic compound in the area applied with toner cannot color (color less) and the non-imaged area is colored by the coloring of photochromic compound on irradiating the whole surface with ultraviolet rays resulting in a negative image as'a whole and the difficult distinguishing of image. The image is reproduced by the whole surface exposure to ultraviolet ray.

As such resin toners, there may be used resins which are not preferable as binders for the photochromic sensitive material, e.g. polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinyl acetate copolymer, polyhydroxyethylmethacrylate and polyvinylpyrrolidone.

(ii) When an image is developed with a toner that color develops the photochromic compound due to the polarity when a transparent resin free from color pigment is mixed with said compound, the sensitive layer is mixed with the toner layer to yield a colored positive image even in the dark. In this case also, the non-imaged area may be colored by the whole surface exposure. As such toners, there are mentioned for example cellulose acetate, ethyl cellulose, cellulose acetate butylate, cellulose acetate phthalate etc.

(iii) When a toner is used in which the mixture of transparent resin free from color pigment and a photochromic compound does not color as it is but colors on irradiating light and the development in the area applied with the toner is quite different from that in the nonimaged area, an image is obtained which is diflicultly distinguished by eyes in the dark but has different shades from other areas on whole surface exposure.

, As these toners, there are mentioned mixtures of resins such as polystyrene, polyvinyl acetate and polymethacrylate with a third substance. As said third substances, there are preferably compounds having a large polarity which are different from that of said resins with preference for aromatic carboxylic acids and phenols but which are not restricted only to these compounds. For example, there are mentioned phthalic acid, benzoic acid, nitrobenzoic acid, chlorobenzoic acid, oxybenzoic acid, salicylic acid, toluylic acid, naphthoic acid, anthranilic acid, anisic acid, nitrophenol, naphthol, picric acid, chlorophenol oxyacetophenone, resorcin, hydroquinone, oxybenzophenone etc.

(iv) When a toner containing. colored pigment is used, the color of image area may be varied according to the preference and converted into a positive image, in which the non-imaged area is colored, by the whole surface exposure to ultraviolet rays. The toners to be used thereto are not restricted to resins of (i)(iii) and they may be used as toners by adding colored pigment or colorants to these resins.

For example, the following pigments or coloring mat-j ters are selected resulting in giving any desired colored toner:

Black: Carbon black.

Red: Brilliant Carmine 6B, Quinacridone Red, Oil red.

Yellow: Hausa Yellow, Benzidine Yellow, Oil Yellow.

Blue: Phthalocyanine Blue, Phthalocyanine Green.

Other than these groups, the combination of photochromic compound and toner resin can provide any desired color image, occasionally resulting in a variously varying shade of tonered area.

In this invention, a monochromic or multi-color image is obtained by utilizing the function of said four kinds of toners; for example, a sensitive material is treated first with a toner of the group (i), the material carrying the first toner image is again charged in the dark and imagewise exposed to yield the second latent image, which is then developed with a toner of the group (ii), resulting in an image which consists of three areas of different shades, i.e. the non-imaged area, the first toner image area (colorless) and the second toner image area (the second shade different from that of the non-imaged area). In this case, the first toner image area, when the toner is highly insulating, is charged at a high voltage and the light decay is rather delayed, so that the second toner may be apt to strongly adhere again to the first toner image area (in the positive-positive development). This gives no influence to the shade of image at all providing no problem where the second toner is also colorless.)

Very advantageously, the photochromic compound contained in the sensitive layer of this invention not only behaves to provide an imlage of more than one color in the development but sensitizes the photosensitivity of a photoconductor such as poly-N-vinyl carbazole, i.e. behaves as a sensitizer. As photochromic compounds to be used in this invention, there are mentioned those represented by the following general formula:

wherein R represents alkyl radical ha ving 1-5 carbon atoms, substituted alkyl (substituent: carboxyl, cyano or ester group) or phenyl radical, R and R represent alkyl radical having 1-5 carbon atoms or phenyl radical or may form together (CH n is 4 or 5, X represents hydrogen atom, nitro group, halogen atom; hydroxycarbonyl and alkoxycarbonyl group, alkyl radical ha'ving 1-5 carbon atoms or alkoxy group, and Y represents at least more than one of hydrogen atom, nitro group, halogen atom, aldehyde group and alkoxy group.

As compounds of the above general formula, there are given the following compounds:

1 3, 3-trimethylspiro (indoline-2,2'-2'-H-chromene) 1 ,3, 3-trimethyl-8'-formylspiro (indoline-2,22-H- chromene) 1,3,3-trimethyl-6',8'-dichlorospiro(indo1ine-2,2'-2'H- chromene) 1, 3, 3 -trimethyl-8-methoxyspiro (ind-oline-2,2'-2'H- chromene) 1 ,3,3-trimethyl- 6'-nitrospiro (indoline-2,2'-2'-H- chromene) 1,3,3-trimethyl-6', 8-dibromospiro (indoline-2,2'-2'H- chromene) 1, 3 ,3-trimethyl- ,7'-dichloro-6--nitro spiro (indoline-2,2'- 2'-H-chromene) 1,3 ,3 -trimethy1-8 '-formyl-6-nitrospiro (indo1ine-2,2'-

ZH-chromene) 1,3,3-trimethy1- '-methoxy-6'-nitrospiro (indoline-2,2'-

ZH-chromene) 1-ethyl-3 ,3-dimethyl-6-nitro spiro (indoline-2,2'-2'H- chromene) 1-propyl-3, 3-dimethy1-6'-nitrospiro (indoline-2,2'-2'H- chromene) 1-butyl-3,3'dimethyl-6'-nitrospiro (indoline-2,2-2H- chromene) 1,3 ,3-trimethy1-5 -methyl-6'-nitrospiro (indo1ine-2, 2-2'H- chromene 1,3 ,3-trimethyl- S-methyl-8'-methoxy-6-nitrospiro- (indoline-Z,2'-2'H-chromene) 1,3 ,3-trimethyl-5-methyl-5 ',7 '-dichloro6'-nitro spiroindoline-2,2-2'H-chromene) 1, 3 3 -trimethyl-5-methoxyspiro (indoline-2,2'-2-H- chromene) 1,3,3 -trimethyl-5-methoxy-6-nitrospiro(indoline-2,2'-

ZH-chromene) 1,3,3 -trimethyl-5-methoxy-8'-methoxy-6'-nitro spiro- (indoline-Z,2'-2H-chromene) 1,3, 3-trimethy1-5-chlorospiro (indoline-2,2'-2'H- chromene 1,3 ,3-trimethyl-5-chloro-6'-nitrospiro (indoline-2,2'-2'H- chromene) 1,3 ,3-trimethyl-5-chloro-8-methoxy-6'-nitrosporoindoline-2,22H-chromene) 1,3,3-trimethyl-5-chloro-6',8-dibromospiro (indoline-2,2'-2'H-chromene) 1, 3, 3-trimethyl-5-nitrospiro (indoline-2,2'-2'H- chromene) 1,3, 3-trimethyl-5,6-dintrospiro (indoline-2,2-2'H- chromene 1, 3 ,3 -trimethyl-5 ,6'-dinitro-8 methoxyspiro (indoline- 2,2'-2'H-chromene) 1,3,3-trimethyl-5-nitro-6',8'-dibromospiro (indoline- 2,2'-2'H-chromene) 1, 3, 3-trimethyl-5-ethoxycarb onyl-6-nitrospiro (indoline-2,22H-chromene) 1, 3 3-trimethyl-5-ethoxycarb onyl- '-methoXy-6'-nitrospiro (indoline-Z,2-2'H-chromene) 1, 3 ,3-trimethyl-5 -ethoxycarbonyl-6,8 -dibromospiroindoline-Z,2'-2'-H-chromene) 1-benzyl-3 ,3-dimethyl-8'-methoxy-6'-nitrospiro (indoline-2,2'-2'H-chromene) 1-benzyl-3 ,3 -dim'ethyl48 '-nitrospiro (indoline-2,2'-2'H- chromene) 1-carboxyethyl-3,3 -dimethyl-6'-nitrospiro (indoline- 2,2-2'H-chromene) 1-carboxyethyl-3 ,3 -dimethyl-8 '-methoXy-6-nitrospiro- (indoline-2,2'-2'H-chromene) 1-cyanoethy1-3 ,3-dimethylspiro (indoline-2,2'-2'H- chromene) 1-cyanoethyl-3, 3-dimethyl-6-nitrospiro (indoline- -2,2'-2H-chromene) 1-cyanoethy1-3 ,3 dimethyl- 8 -methoxy-6'-nitrospiro- (indoline-2,2'-2'H-chromene) 1-carboXypropy1-3 ,3-dimethyl-6'-nitrospiro (indoline- 2,2'-2'H-chrom'ene) 1-carb0xypropyl-3 3-dimethyl-8 methoxy-6'-nitr0spiroindoline-2,2-2'H-chromene) l-y-carboethoxypropyl-3 ,3-dimethylspiro (indoline- 2,2'-2'H-chromene 1-'y-carboethoxypropyl-3,3-dimethyl-6'-nitrospiro (indoline-2,2'-2'H-chromene) 1-7-carboethoxypropyl-3 ,3 -dimethyl-8-methoxy-6- nitrospiro (indoline-2,2-2'H-chromene) l-w-bromobutyl-3,3-dimethylspiro (indoline-2,2'-2 H chromene) 1-w-bromobutyl-3, 3 -dimethyl-6'-nitrospiro (indoline- 2,2-2'H-chromene) 1-w-bromobutyl-3 ,3-dimethyl-8 '-methoxy-6'-nitrospiro indoline-Z,2'-2'H-chromene) 3, 3-dimethyll-hydroxyethylspiro (indoline-2,2-2H- chromene) 1,3-dimethyl-3-ethylspiro (indoline-2,2-2 'H- chromene) 1,3-dimethyl-3-ethyl-6'-nitrospiro(indoline- 2,2-2H-chromene) 1 7 1,3-dimethyl-3-ethyl-8'-methoxy-6'-nitrospiro(indoline-2,2-2'H-chromene) H r 1,3-dimethyl-3-phenyl-6-nitrospiro(indoline- 2-2'-2'H-chromene) v 1-methyl- 6-nitro-2H-chromene-2'spiro-2'indoline- 3'-spiro-1"-cyclohexane 1'-methyl-6'-nitro-2H-chromene-2-spiro-2'-indoline- 3'-spiro-l"-cyclopentane As resins having photoconductivity, there are mentioned the following two groups of compounds:

(1) Polynucleus aromatic vinyl polymers :"poI'ym'ers of vinyl naphthalene, vinyl anthracene, vinyl diphenyl, vinyl :fiuorene, vinyl acenaphthene, vinyl -p'yrene, vinyl naphthacene, vinyl perylene etc. (2) Vinyl polymers having a heterocyclic side chain: polyvinylcarbazole, polyvinylphenothiazine, polyvinylacridine, polyacryloylcarbazole," .polyvinylbenzofuran, polyvinylpyrazoline, polyvinyloxazole, polyvinyl-fluorine etc.

Preferably, the amount of the photochromic compound to be used in this invention is 01-10% by weight referred to the photoconductive resin, above all preferably 25%.

As the developers for the formation of an image according to the electrophotographic process, those of either cascade development or liquid development may be used. 1 1

For example, a colorless liquid developerniay' be preparedby the'following procedure:

' Part si(by weight) i 2 Polyvinyl acetate Linseed oil-modified alkyd resin 5 Butyl acetate .30 Toluene 5 parts of the mixed solution of above components are added dropwise to the mixture of Parts Kerosene 285 Cottonseed oil ,s,r .9t ia which mu r the prepa a on otp itive or negative developers. Colorrdpigments, dye or other additives can be added to these to yield toners corresponding to the purposes.

For the formation of a sensitive layer, the solution of V photochfomi'c compound and photoconductive resin dissolved in a suitable organic solvent is coated on a support such as transparent film or paper, etc., which is subjected to the conduction treatment, and dried. The product which is obtained by the process according to this invention may be applied to the multicolor copy, display, original for overhead projector, decoration film, etc. and is considerably excellent for fixing of photochromic sensitive material.

This invention will be illustrated more fully by the following examples.

EXAMPLE 1 A solution consisting of 1 part of 1,3,3-trimethyl-5- ethoxycarbonyl-6'-nitrospiro(indoline 2,2 Z'H-chromene) and 50 parts of toluene solution of poly-N- vinylcarbazole was coated on a polyethylene terephthalate film providedwith a transparent conductive undercoat so that the dry film thickness may be 10 1.. The film is ordinarily colorless and transparent. The sensitive layer may be'used in the following two ways:

(i) A transparent negative image film is contacted to the layer and irradiated for 30 sec. by an ultraviolet lamp (Toshiba 'SI IL-IOO, manufactured by Tokyo Shibaura Electric Co.,Ltd.) at a distance of 15 cm. to yield a positive image which is colored only in the areas through which ultraviolet rays have passed. If it is stood in the dark or heated at C., it returns to a colorless transparent film.

(ii) The colorless film is charged positive in the dark, contacted with a transparent positive image film, exposed for 2.secs. by a 20 w. fluorescent lamp (Toshiba Neoline FL -ZOS, Manufactured by Tokyo Shibaura Electric Co., Ltd.) at a distance of 15 cm. and developed with a liquid colorless toner developer having a negative charge (e.g., liquid developer containing polyvinyl chloride as a toner) to yield a positive image in which the areas provided with the toner are opaque. When it is placed in a vapor atmosphere ofv solvent which dissolved the. toner, such as trichloroethylene, it becomes transparent and is fixed. The .image is distinguished diincultly by eyes. When it is overall irradiated for 30 sec. by anultraviolet lamp, the nonimaged area is colored blue to yield a negative image in which'the toner developed image area is transparent. If it is stoodin the dark or heated, it is discolored to transparent. Example 1 belongs to the above mentioned-classificat ion (i). EXAMPLE 2 .A solution consisting of 1 part of 1,3,3-trimethyl-6'- nitrospiro (indoline-2,2-2'H-chromene) and 50 parts of 20% toluene solution of poly-N-vinylcarbazole is coated on a polyethylene terephthalate film provided with a transparent conductive undercoat so that the dry film thickness may be 10p. It shows the previousphotochromism. The film is further charged in the same manner asin Example 1 accordingto the electrophotographic process, exposed imagewise, developed with a cellulose triacetate toner and fixedin theatmosphere of trichloroethylene to yieldan image inwhich the image area is red and the non-imaged area colorless. If it is over-all'exposed to ultraviolet rays, the non-imaged area becomes dark blue and the image area reddish violet. This example belongs to theaboveclassification (ii). .In this example, the variation of toner components (additives and resin) provided the results as shown in the following table.

- Over-all exposure to In the dark ultraviolet rays Color of Color of Color of Color of unimaged image unimaged image Additive Resin area area area area PMMA Colorless Colorless Blue Reddish purple. PVAc do do Pink. TAG 3 do Rod do Reddish purple- PMMA do Colorless-...' ..do Pink.

p-Oxybenzoic acid PVAe do do do Do.

TAG -do pale yellow "do Bluish purple. PS -..-do Colorless .-do Bink. PMMA do do do Do.

Tinuvin 326 I PVAc D TAC PS PMMA Uvinul M-40 PVAc d Do.

TAO --.--do Pale yellow ..do..-. Reddish purple. PS do Colorless-.. do Bluish purple. PMMA do Pale red do Pink.

p-Nltrophenol PVAC --.-do Colorless.-.-: .-do Red.

TAO -.do Pale yellow .do Reddish purple. PS do do Bluish purple. PMMA do Yellow do Purple.

Carbontetrabromlde PVAe do do do Orange.

'IAC do do do Yellow.

(in do do Do,

PS X Pl\4MA=Polymethylmethacrylate. PVAc=Polyvinyl acetate. I TAG Cellulose triacetate. l PS=Polystyrene. 5 Tlnuvin 326=Ultravio1et absorber manufactured by Geigy Co. Uvinul M-40= Ultraviolet absorber manufactured by GAF Co. 7 The term colorless" means colorless and transparent."

EXAMPLE 3 The sensitive material obtained in Example 1 is developed with a toner of p-oxybenzoic acid and polymethylmethacrylate, fixed and over-all exposed to ultraviolet rays, whereby the nonimaged area is colored blue and the image area pink. It turns to colorless and transparent on heating at 80 C.

This example belongs to the above classification (iii).

EXAMPLE 4 A solution consisting of 1 part of l,3,3-trimcthyl -51 methoxy-6'-nitrospiro (indoline-Z,2'-2'H-chromene) and 50 parts of toluene solution of polyacenaphthylene is coated on a polyethylene terephthalate film provided with a transparent conductive under-coat so that the dry film thickness may be 10;, and dried to yield a transparent film, which shows of course the previous photochromism. The film is charged and exposed in the same manner as in Example 1, cascade-developed with a blue toner and fixed to yield a positive image. I

When it is over-all exposed to ultraviolet rays, the whole surface turns to blue resulting in the difficult distinguishing of image. When it is heated, the nonimaged area becomes colorless resulting in a distinct image.

This example belongs to the above classification (iv).

What is claimed is:

1. A process for the formation of a toner image by an electrophotographic process comprising the steps of:

(a) forming an electrostatic latent image by uniformly charging and imagewise exposing an electrophotographic sensitive layer containing a photochromic compound, and

(b) developing and solvent fixing said image with a transparent toner free from color pigment which will interact with said photochromic compound to control the color thereof,

thereby forming a toner image.

2. The process of claim 1, wherein said toner is a resin capable of interacting with said photochromic compound upon contact to cause said photochromic compound-to change color.

3. The process of claim 1, wherein said photochromic compound is a compound represented by the general formula wherein R represents alkyl having 1-5 carbon atoms, substituted alkyl wherein said substituents are carboxyl, cyano or ester groups, or phenyl; R and R are alkyl having 1-5 carbon atoms, phenyl or they form together (CH n is 4 or 5, X represents hydrogen, nitro, halogen, hydroxycarbonyl, alkoxycarbonyl, alkyl having 1-5 carbon atoms or alkoxy; and Y represents at least more than one of hydrogen, nitro, halogen, aldehyde and alkoxy.

4. The process of claim 14, wherein said photochromic compound is 1,3,3-trimethyl-6'-nitrospiro(indoline-2,2'- 2H-chromene) and said toner is cellulose triacetate.

5. The process of claim 1, comprising the further step of exposing the entire surface of said electrophotographic sensitive layer to ultraviolet radiation after saiddeveloping' step.

6. The process of claim 1, wherein said toner comprises a combination of a resin and an additive which together are capable of interacting with said photochromic compound upon contact to cause said photochromic compound to change color.

7. The process of claim 5, wherein said resin is cellulose triacetate and said additive is chosen from the group consisting of p-oxybenzoic acid, p-nitrophenol and carbon tetrabromide.

8. The process of claim 6, wherein said resin is chosen from the group consisting of polymethylmethacrylate and polystyrene ,and said additive is selected from the group consisting of p-nitrophenol and carbon tetrabromideo 9. The process of claim 7, wherein said resin is polyvinyl acetate and said additive is carbon tetrabromide.

10. The process of claim 5, wherein said toner is a resin selected from the group consisting of polymethylmethacrylate, polyvinylacetate and cellulose triacetate.

11. The process of claim 5, wherein said toner is a resin selected from the group consisting of polymethylmethacrylate, polyvinylacetate, cellulose triacetate and polystyrene together with an additive selected from the group consisting of p-oxybenzoic acid, p-nitrophenol and carbon tetrabromide.

12. A process for the formation of image according to claim 1 characterized in that a resin which hinders the color-development of said photochromic compound is used as the resin toner.

13. A process for the formation of image according to claim 12 characterized in that as said resin toner there is used polyvinyl chloride, polyvinylidene chloride, vinyl chloride/vinyl acetate copolymer, polyhydroxyethylmethacrylate or polyvinyl-pyrrolidone.

14. A process for the formation of image according to claim 15, wherein said resin is selected from the group consisting of cellulose acetate, ethyl cellulose, cellulose acetate butylate or cellulose acetate phthalate.

15. A process for the formation of a toner image ac cording to claim 1 wherein said toner is a mixture of a resin and a compound having a larger polarity than said resin, which mixture will interact with said photochromic compound upon exposure to ultraviolet radiation to form a color which is difierent than the color formed by said photochromic compound upon ultraviolet radiation in the absence of said mixture.

16. A process for the formation of image according to claim 15 characterized in that polystyrene, polyvinyl acetate or polymethacrylic acid ester is used as said resin.

17. A process for the formation of image according to claim 15, wherein said compound is selected from the group consisting of phthalic acid, benzoic acid, nitrobenzoic acid, chlorobenzoic acid, oxybenzoic acid, salycilic acid, toliylic acid, naphthoic acid, anthranilic acid, anisic acid, nitrophenol, naphthol, picric acid, chlorophenol, oxyacetophenone, resorcin, hydroquinone or oxybenzophenone.

References Cited J. TRAVIS BROWN, Primary Examiner J. R. MILLER, Assistant Examiner US. Cl. X.R.

1.2, 1.5, 1.6, PC; 117-17.5, 37 LE;

96-1 SD, 1 LY, 

